North American coral snakes aren’t aggressive, and are responsible for less than 1 percent of snake bites in the US. However, their venom contains a potent neurotoxin that can impair breathing. Coral snakes have red, black, and yellow (or white) rings. This bright warning coloration, a type of aposematism, protects them from predators, who learn to avoid snakes with such patterns.
There are several harmless snake species, including milk snakes and scarlet kingsnakes, that have evolved similar markings, allowing them to avoid being eaten without expending energy on venom production. Imitating a harmful species’ warning signals is known as Batesian mimicry, after the English naturalist Henry Walter Bates.
Although these snakes all have red, black and yellow transverse stripes, on the coral snake, red and yellow bands are adjacent to one another, and on innocuous snakes, red and black bands are adjacent. There are a few variations on a mnemonic that can be used to distinguish between venemous and non-venemous species:
- Red to yellow, kill a fellow. Red to black, venom lack.
- Red and black, friend of Jack; red and yellow kill a fellow.
- Red next to black, poison I lack; red next to yellow, run away fellow.
This rule only reliably applies to North American coral snakes; coral snakes from other regions can sport a variety of patterns, including some with red bands touching black bands.
|Feature||Coral snake||Milk snake||Scarlet kingsnake|
Eastern - Micrurus fulvius
Texas - Micrurus tener
Arizona - Micruroides euryxanthus
|Lampropeltis triangulum||Lampropeltis elapsoides|
|Average length||60 to 90 cm||50 to 150 cm||35 to 50 cm|
|Distribution||southeastern United States and Arizona||southeastern Canada to northern South America||southeastern United States|